Dry eye, also known as keratoconjunctivitis sicca, is a common ophthalmological disorder affecting millions of Americans each year. The condition is particularly widespread among post-menopausal women due to hormonal changes following the cessation of fertility.
Dry eye may afflict an individual in varying severity. In mild cases, a patient may experience burning, a feeling of dryness, and persistent irritation such as is often caused by small bodies lodging between the eye lid and the eye surface. In severe cases, vision may be substantially impaired. Good reviews of the dry eye syndrome and standard methods of treatment may be found in Dohlman (1971) and Lemp (1973).
Although it appears that dry eye may result from a number of unrelated pathogenic cause, all presentations of the syndrome share a common effect, that is the breakdown of the pre-ocular tear film, which results in dehydration of the exposed outer surface and many of symptoms outlined above.
Practitioners have taken several approaches to the treatment of dry eye. One common approach has been to supplement and stabilize the preocular tear film using so-called artificial tears. Another approach has been the use of ocular inserts that function variously to provide a tear substitute or to stimulate endogenous tear product.
Examples of the tear substitution approach include the use of buffered, isotonic saline solutions, aqueous solutions containing water soluble polymers that render the solutions more viscous and thus less easily shed by the eye. Tear reconstitution is also attempted by providing one or more components of the tear film such as phospholipids. Examples of these treatment approaches are disclosed in U.S. Pat. Nos. 4,131,651 to Shah et al.; 4,370,325 to Packman; 4,409,205 to Shively; 4,744,980 and 4,883,658, both to Holly; 4,914,088 to Glonek; and 5,057,104 to Gressel et al.
United States Patents directed to the use of ocular inserts in the treatment of dry eye include U.S. Pat. No. 3,991,759 to Urquhart. The use of ocular inserts is also discussed in detail in Lamberts (1980).
Another recent approach involves the provision of lubricating substances in lieu of artificial tears. U.S. Pat. No. 4,818,537 to Guo discloses the use of a lubricating, liposome-based composition. U.S. Pat. No. 4,966,773 discloses the use of microfine particles of one or more retinoids.
Aside from the above efforts, which are directed primarily to the alleviation of symptoms associated with dry eye, also known are methods and compositions directed to treatment of the dry eye condition. For example, U.S. Pat. No. 5,041,434 discloses the use of sex steroids, such as conjugated estrogens, to treat dry eye condition in post-menopausal women.
Although these approaches have met with some success, problems in the treatment of dry eye nevertheless remain. The use of tear substitutes, while temporarily effective, generally requires repeated application over the course of a patient's waking hours. It is not uncommon for a patient to have to apply artificial tear solution ten to twenty times over the course of the day. Such an undertaking is not only cumbersome and time consuming, but is also potentially very expensive.
The use of ocular inserts is also problematic. Aside from cost, they are often unwieldy and uncomfortable. Further, as foreign bodies, they run a risk of infection to the eye. In situations where the insert does not itself produce and deliver a tear film, artificial tears must still be delivered on a regular and frequent basis. Indeed, Pavan-Langston (1973) has concluded that, as a rule, ocular inserts are not very effective in the treatment of many dry eye conditions.
In view of the foregoing, there is a clear need for an effective treatment for dry eye that is capable of alleviating symptoms, as well as treating the underlying physical and physiological deficiencies of the syndrome, and that is both convenient and inexpensive to administer.